Stored product pests such as Tribolium castaneum ( Herbst, 1979) are a major problem. Adult insects were obtained from laboratory cultures maintained in the dark in incubators at 25± 1C and 70–80% r.h., reared on wheat flour and fed with flour disks containing a known concentration of essential oil of 9 plants. The chemical components of essential oil of 3 plants, collected on the area of Montenegro, were also identified using GC-MS analysis. The results of insecticidal effect of essential oils were discussed. Also, mortality rate of adult insects was tested. In this research, the essential oils of C. glandulosa which were rich in monoterpene alcohols carvacrol and contained ketonic component showed strong insecticidal and fumigant activity against adults of T. castaneum. Less toxic effect showed essential oils of Satureja montana which had a lower carvacrol and ketonic content. On the other hand, essential oils of Teucrium polium which did not contain ketonic component did not show any activity. Therefore, it was observed that essential oils of C. glandulosa with concentration of 1.14% showed powerful toxic and repellent effect, with very high mortality rate after 24h (56,67%).
